Method of interconnecting glass parts by passing through electric current

ABSTRACT

In sealing glass parts to each other by passing electric current through the preheated glass edges, the electric current is supplied to the glass edges via a stream of rare gas.

United States Patent 1191 Van Duuren et al.

1 111 3,816,087 1 June 11, 1974 METHOD OF INTERCONNECTING GLASS PARTS BYPASSING THROUGH ELECTRIC CURRENT [75] lnventors: Kars Van Duuren;Adrianus Cornelis Johannes Verhoeven, both of Emmasingel, Eindhoven,

Netherlands [73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: Oct. 12, 1971 [2]] App]. No.: 188,614

Related US. Application Data [63] Continuation of Ser. No. 8,325, Feb.3, I970,

abandoned.

[30] Foreign Application Priority Data Netherlands 6902027 Feb. 8, 1969[52] [1.8. CI. 65/40, 65/152, 219/121 P [51] Int. Cl C031) 29/00 [58]Field of Search 65/40, 152; 219/121 P [56] References Cited UNITEDSTATES PATENTS 12/1942 Guyer 65/40 10/1958 Gage 219/121 P x PrimaryExaminer-Robert L. Lindsay, Jr. Attorney, Agent, or FirmFrank R. Trifari[57] ABSTRACT In sealing glass parts to each other by passing electriccurrent through the preheated glass edges, the electric current issupplied to the glass edges via a stream of rare gas.

3 Claims, 2 Drawing Figures 1 METHOD OF INTERCONNECTHNG GLASS PARTS BYPASSING THROUGH ELECTRIC C 1:

This application is a continuation of application Ser. No. 8,325, filedFeb. 3, 1970, now abandoned.

The invention relates to a method of interconnecting glass parts byfusing their edges together, in which the joined, preheated edges areheated and caused to fuse together by the passage of electric currentwith the aid of current supply points arranged along the outercircumference.

It is known, for example, from British Pat. specification No. 885,195 touse the flames of gas burners as current supply points. It has beenfound, however, that a few disadvantages may be involved. It may occurthat the arc is unsteady so that a broader strip of glass is heated thanrequired. Moreover, the arc may stand still for some time at a givenpoint of the glass surface, although the glass surface is movedrelatively to the current supply point. This gives rise to localoverheating and decomposition of the glass.

In order to avoid these disadvantages British Pat. specification No.985,422 proposes to surround the gas flame conveying the electriccurrent by flow of nonionized gas, for example, cold air, However, thismethod is complicated.

It has been found that said disadvantages can be completely obviated byusing in accordance with the invention as a current supply point astream of a rare gas. It is preferred to use argon as a conductive gasfor the electric current.

The invention will be described more fully with reference to anembodiment and to the drawing, in which FIG. 1 is a schematic crosssectional view and H6. 2 is a schematic longitudinal sectional view ofan assembly for interconnecting glass parts of the bulb of an electrontube.

In the drawing reference numeral 1 designates the glass cone of anelectron tube, to which a flat glass window 2 has to be sealed. The cone1 is clamped in a holder and the glass plate 2 in a holder 111, whichholders can be caused to rotate.

After the edges of the bulb parts 1 and 2 to be sealed together havebeen heated by means of gas burners 3 and tat about 600C, a rare gas, inthis case argon is supplied to the copper tubes 5 by means of the hoses6 of insulating material, while an alternating voltage is applied to thetubes 5 by means of the conductors 9. The tubes 5 are adjustedpreviously by means of the clamping connection 8 so that theirmouthpieces are at a distance of about 0.5 to 2 cm from the glass edgesof the bulb parts 1 and 2 to be sealed. The argon stream is sufficientlyconductive in the cold state for conveying the electric current to thepre-heated glass edges. By this electric current the argon gas israpidly heated so that an arc 12 is struck as in the case of the currentsupply via a gas flame in the known methods. In the embodiment shown,the bulb 1 has a wall thickness of 2 mm, the window 2 has a thickness of4 mm. The alternating voltage is initially about 7,000 V.cm with an arclength of about 0.5 cm on either side of the window 2 and after heatingof the argon stream and the glass it drops to about 1,500 V. Thesevalues correspond approximately with those involved in the use of a gasflame for current supply. The argon stream has in this case a sectionalarea of 1 mm, whilst about 2 litres of argon are consumed per minute ateach supply point.

In contrast to the known methods, in which the are passed along a gasflame reciprocates unsteadily, the arc struck via an argon stream isalmost completely already and does not tend to stick to given points ofthe weld so that burned-in dots in the weld are avoided.

The current strength through the arcsand the glass edges is initially 8Amp. but it is afterwards raised to about 14 Amp. at which the glassbecomes thin liquid. After the edges of the bulb parts 1 and 2 havefused together, the electric current as well as the supply of argon areinterrupted in order to avoid that a cold stream of argon strikes thehot weld, after which the weld is after-heated in a conventional mannerby means of the burners 3 and 4 and is subsequently cooled slowly. Theholder 11, in which the window plate 2 is held, for example, bysubatmospheric pressure, can be moved up and down in a conventionalmanner so that during the preheating process the glass edges of theparts 1 and 2 can be held at a given distance from each other andheating of the outer and inner sides is more uniform. For sealing theedges together, they are simply brought into contact with each other.

The invention is suitable both for sealing together thick glass wallparts, for example, the window and the cone of television display tubesand for interconnecting thin-walled parts, for example, the neck and thecone of such a display tube. The length of the arc and the currentstrength are, of course, adapted to the thickness of the glass as wellas the diameter and the rate of flow of the argon if necessary.

Although only argon is mentioned herein, the other rare gases: neon,helium, krypton and xenon may also be employed. However, argon is foundto provide the best results.

Instead of using two current supply points three or more supply pointsmay be used in a conventional manner, in which case threeor multi-phasealternating current is used. If desired, the glass parts may be sealedtogether whilst they are standing still with respect to the currentsupply points,

The ignition voltage and the arc voltage may be reduced by producing anauxiliary discharge in the gas supply duct or closely in front of thegas outlet aperture so that the gas stream is pre-ionized.

What is claimed is:

1. A- method of interconnecting glass parts by sealing their edges toeach other comprising the steps of:

preheating the edges of the glass parts;

bringing the preheated edges in contact with each other;

passing an electric current through at least two streams of ionized raregas, said streams being arranged circumferential to the edges to besealed and directed at said edges;

and rotating said edges relative to the streams to uniformly heat saidedges by said current to provide an evenly fused glass seal between saidedges.

2. A method as claimed in claim 1, wherein said rare gas is argon.

3. A method as claimed in claim 2 wherein the gas stream is pre-ionizedby an auxiliary discharge.

1. A method of interconnecting glass parts by sealing their edges toeach other comprising the steps of: preheating the edges of the glassparts; bringing the preheated edges in contact with each other; passingan electric current through at least two streams of ionized rare gas,said streams being arranged circumferential to the edges to be sealedand directed at said edges; and rotating said edges relative to thestreams to uniformly heat said edges by said current to provide anevenly fused glass seal between said edges.
 2. A method as claimed inclaim 1, wherein said rare gas is argon.
 3. A method as claimed in claim2 wherein the gas stream is pre-ionized by an auxiliary discharge.